In the image compression field, it is proved that a method for performing intra-frame prediction by using an information correlation between non-adjacent regions can effectively improve prediction quality. An intra-frame predictive coding method based on L-shaped-template matching belongs to this type of method.
A theory hypothesis of the intra-frame predictive coding method based on L-shaped-template matching is as follows: there is a relatively strong texture correlation between image information in a prediction unit and image information in an L-shaped template. However, when a texture of a to-be-compressed image is complex and variable, a correlation between an image texture in a prediction unit and an image texture in an L-shaped template is generally low, and the foregoing theory hypothesis may not valid. In this case, if the L-shaped template is still used to perform intra-frame predictive coding, accuracy of the prediction unit may be reduced.
It can be seen that, when a texture of a to-be-compressed image is complex, how to ensure accuracy of a prediction unit becomes a currently to be resolved problem.